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Coolant effect on grinding performance in high-speed deep grinding of 40Cr Steel
) TECHNICALLY speaK,ng BY ZHENTAO SHANG1'2,HAN HUANG'r2,KUN TANGZ,AND SHAOHUI YIN2, 'SCHOOL OF ENGINEERING,THE UNIVERSITYOF QUEENSLAND, BRISBANE,AUSTRALIA;AND 2NATIONALENGINEERINGRESEARCHCENTREFOR HIGH-EFFICIENCYGRINDING, HUNAN UNIVERSITY,CHANGSHA,CHINA
, ) )c.~ xl,
10
Coolant Effect on Grinding Performance in High-Speed Deep Grinding of 40Cr Steel
H
igh-speed deep grinding (HSDG) technology was developed based on high-speed and creep-feed grinding techniques. 1-3 What mainly distinguishes HSDG from creep-feed grinding is its employment of a significantly higher wheel speed. Because the higher wheel speed results in a decrease in the undeformed chip thickness, HSDG is thus capable of achieving high stock removal rates and producing a high surface quality throughout the workpiece.46 However, the increase in wheel speed leads to the formation of a strengthened air barrier around the grinding wheel periphery, which is a great obstacle to the impinging of coolant into the grinding zone. 78 Additionally, the higher wheel speed will also generate greater grinding heat in the grinding zone, thus resulting in a higher temperature.' This increases the risk of thermal damage on the workpiece, such as burns and cracks, especially when grinding metals and alloys. In order to take advantage of the full potential of HSDG technology, effective cooling must be employed. Great research efforts have been directed toward investigating effective coolant supply technologies for the HSDG process.71° Previous works focused on the development of coolant nozzles for high-speed grinding, which could block the air barrier formation and help smoothly guide the coolant May 2008 1metalfinishing I 16
entering the grinding zone. There are several drawbacks regarding these nozzles. First, a gap between the wheel and the air-wiper in the nozzle still exists, which affects the coolant supply when operating at an extremely high speed. Second, the air blocking alters the coolant flow direction, thus resulting in an increase of 30-50% in spindle power. Third, special grinding wheels are required if there is direct contact between the wheel and the air wiper. This article will report on the development of a "closed" coolant shoe, which can overcome the limitations of previous coolant nozzles, and the effect of the new nozzle on the grinding performance in HSDG of 40Cr steel.
0
-6
Figure 1: Schematic illustrations of (a) conventional L-type nozzle, (b) closed Y-type nozzle, and (c) the detailed layout of the closed Y-type nozzle. (1) Grinding wheel; (2) steel cover; (3) rubber seal; (4) nozzle body; (5) hinge; and (6) adjustable blocker.
~
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150 200 C,rir'~Ltnll speed (.,/s)
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Figure 2A 120 ~100
g
CLOSED Y-TYPE NOZZLE
Figure i shows the comparison of the conventional L-type nozzle and the detailed layout of the newly developed nozzle. As illustrated in Figure 1A, the L-type nozzle has only one orifice. The Y-type nozzle shown in Figure 1B has two orifices. The flow directions of the two orifices have an angle of 60 °, hence its name as "Y-type" nozzle. Figure 1C shows the detailed structure of the "closed" Y-type nozzle. "Closed" here refers to the nearly enclosed cavity formed by
t~ ~ 4o '~ 20 0 100
Figure 2B Figure 2: (A) Specific vertical force and (B) specific horizontal force are plotted as a function of wheel speed. Depth of cut = 1.7 mm; feed rate = 2,000 mm/min.
Table 1: Chemical Composition of 40Cr Steel (wt. %)
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TECHNICALLY speaKing the wheel (1), the rubber seal (3) and the nozzle body (4). The working principle of the nozzle is listed as follows: 1. The m o m e n t u m of coolant from the upper orifice counteracts with the airflows surrounding the wheel, which blocks the air circulating in the grinding zone and allows the coolant to enter the enclosed cavity. Additionally, the coolant from the upper orifice can clean out the wheel as well. 2. Coolant from the lower orifice is mainly sprayed into the grinding zone, functioning like the conventional coolant supply. 3. There is a gap between the wheel and the lower orifice, which acts as the third orifice, so coolant in the enclosed cavity can flow out from this orifice, whose direction can be altered to the grinding zone by the adjustable blocker (6).
EXPERIMENTALDETAILS All the grinding tests were conducted on a super-high-speed surface grinder developed by the National
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, i too
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,
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Figure 3A
, I -'=-- L.t 7pe
150 200 Grin~.r~ Speed (IJs)
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Figure 4: Ground surface roughness is plotted as a function of wheel speed. Depth of cut = 1.7 mm; feed rate = 2,000 mm/rnin
25
0.60 15
~
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Figure 3B
, I -=--L type 1.6 2.0 2.4 Depth ot c,.'t ( n )
Figure 3: (A) Specificvertica[ force and (B) specific horizonta[ force are plotted as a function of depth of cut. Grinding speed = 180 m/s; feed rate = 2,000 ram/rain.
Figure S: Ground surface roughness is plotted as a function of depth of cut. Grinding speed = 180 m/s; feed rate = 2,000 mm/min.
Engineering Research Centre for High-Efficiency Grinding in China. The spindle power of the machine was 40 kW, which enabled our group to run a wheel of 350 mm in diameter up to 24,000 rpm. 40Cr steel was selected as the workpiece
material, and its chemical composition is shown in Table 1. The workpieces were 30 mm long, 7.5 mm wide, and 15 m m thick. The grinding occurred on a 30 x 7.5 m m 2 surface. We used an electroplated cubic boron nitride (CBN) wheel of
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May 2008 1metalfinishing I 17
TECHNICALLY speaking
2.50 2.00
~I.00
!
~
0.50 O.O0
Grindii~g Speed (m/s)
mesh size of 120 that had a diameter of 350 mm and a width of 16 mm. An upward grinding mode was employed. The table feed rate was fixed at 2,000 mm/min, and wheel speeds and depths of cut varied. Grinding tests were carried out using the closed Y-type nozzle and the conventional L-type nozzle, respectively. Grinding forces were monitored using a dynamometer (Kistler 9257B). The surface roughness was measured using a profilometer (Hommelwerke T8000). Surface topographies were examined using a scanning electron microscope (JSM-5610LV).
Figure 7: The maximum depths of cut prior to the onset of thermal damage obtained using the two nozzles. Grinding speed = 180 m/s; feed rate = 2,000 mm/min.
Figure: 6A
Figure: 6B
RESULTS AND DISCUSSION
Figure 6: SEM micrographs and photos of the surfaces ground using (A) the dosed Y-type nozzle and (B) the conventiona| L-type nozzle. Grinding speed = 180 m/s; feed rate = 2,000 mm/min; and depth of cut = 1.7 mm.
Grinding Forces: Figure 2 shows the effect of wheel speed on a specific grinding force when both the depth of cut and the feed rate of the workpiece were kept unchanged. It illustrates that both the specific vertical and horizontal forces decrease with an increase in wheel speed. It is well documented that in high-speed grinding, an increase in wheel speed leads to a reduction in the maxi-
mum undeformed chip thickness, 1 thus resulting in a decrease in grinding forces. Figure 3 shows the effect of depth of cut on the specific grinding force. It is seen clearly that the depth of cut has insignificant influence on the forces. This may be attributed to the relatively small variation in depth of cut. The thermal damage in the high-speed grind-
ing of 40Cr steel was sensitive to the depth of cut, especially when the Ltype nozzle was used, which significantly limited the range of selection for depth of cut. In Figures 2 and 3, it is clearly seen that both specific vertical and horizontal grinding forces using the Ytype nozzle are greater than those using the L-type nozzle for the same grinding conditions. It is worthy to point out that for the conventional L-type nozzle, the ground surfaces were thermally damaged. This suggests that when using the L-type nozzle, the poor cooling effect led to a higher temperature in the grinding zone and hence the thermal damage caused on the ground surfaces. As a consequence, the workpiece material was softened, thus resulting in a decrease in grinding force. SURFACE TOPOGRAPHIES
Figures 4 and 5 show the average roughness of the ground surfaces,
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TECHNICALLY speaKing plotted as a function of wheel speed and depth of cut, respectively. In Figure 4, an increase in wheel speed resulted in a better surface finish. As mentioned earlier, an increase in wheel speed leads to a decrease in chip thickness; therefore, it is expected that the grinding grooves produced were shallower and the surface roughness value was smaller. Again, there was little effect of depth of cut on the surface roughness for the grinding conditions employed, as shown in Figure 5. For all the grinding conditions used, the surface roughness values obtained using the closed Y-type nozzle were smaller than those obtained using the conventional L-type nozzle, as shown in Figures 4 and 5. This is because the burns and cracks generated on the workpiece, due to the poor cooling effect when using the L-type nozzle, deteriorated the surface finish. Figure 6 shows two SEM micrographs and photos of the typical ground surfaces generated using the closed Y-type nozzle and the L-type nozzle respectively, while the rest of the grinding conditions remained the same. It is evident in Figure 6A that the surface ground using the L-type nozzle has cracks and rough plowing grooves near the thermally damaged region. The localized burn is severe and introduces mismatch of strain between hard oxide inclusions. In Figure 6B, when the closed Y-type nozzle was used, no burns and thermal damages were observed on the ground surface, demonstrating excellent surface integrity. MAXIMUM DEPTH OF CUT PRIOR TO THE ONSET OF THERMAL DAMAGE Figure 7 shows the comparison of the maximum depths of cut for the onset of thermal damage obtained when using these two respective nozzles. When grinding 40Cr steel at a high speed of 180 m/s, the L-type nozzle did not function well, as thermal damage was evidently observed on the ground surface when the depth of cut was only at 0.1 mm. Apparently, the application of the closed Y-type nozzle significantly improved the coolant supply to the grinding zone. The maximum depth of cut used prior to the onset of thermal damage is 2.3 mm, considerably greater than that using the L-type nozzle. The results suggests that without the effective coolant supply, it is impossible to employ HSDG technology for 40Cr steels. CONCLUSIONS The closed Y-type nozzle has been successfully developed for high-speed deep grinding of 40Cr steel. The new nozzle used the coolant flow jet from the upper orifice to wipe the air barriers around the wheel periphery at high speeds, which allowed the coolant from the lower orifice to enter the grinding zone and effectively remove the grinding heat. Compared to the www.meta[finishing.com
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May 2008 1metalfinishing I 19
TECHNICALLY
under its KeyResearch Project Scheme (10421), the Australia Research Council under the Discovery Project Scheme (DP0557349), and the Australia-China Science Linkage Program (CN070077).
s p e a k i n g
conventional L-type nozzle, the new nozzle significantly improves grinding performance and the ground surface quality because:
NOTES 1. Tawakoli T. High Efficiency Deep Grinding. London: Mechanical Engineering Publications Ltd., 1993. 2. Huang H, Liu YC. Experimental investigations of machining characteristics and removal mechanisms of advanced ceramics in high speed deep grinding. International Journal of Machine Tools ~ Manufacture 2003;43(8): 811-23. 3. Huang H. Machining characteristics and surface integrity ofyttria partially stabilized zirconia in high speed deep grinding. Materials Science and Engineering 2003;A345:155-63. 4. Ramesh K, Huang H. Burr con-
1. The ground surface roughness obtained using the Y-type nozzle was much smaller than that obtained using the conventional L-type nozzle; and 2. The maximum depth of cut prior to the onset of grinding thermal damage for the Y-type nozzle was 23 times higher than that for the conventional L-type nozzle. ACKNOWLEDGEMENTS The authors would like to acknowledge the experimental assistance of Mr. G.H. Zhang at Hunan University. This project is financially supported by the Ministry of Education, China,
trolled grinding using wheel speed parameter. Metal Finishing 2003;101:57-61. 5. Huang H, Yin L. Grinding characteristics of engineering ceramics in high speed regime. International Journal of Abrasive Technology 2007;1(1):78-93. 6. Yin L, Huang H, Ramesh K, Huang T. High speed versus conventional grinding in high removal rate machining of alumina and alumina-titania. International Journal of Machine Tools & Manufacture 2005;45(6): 897-907. 7. Ebbrell S, Wooley NH, Tridimas YD. The effects of cutting fluid application methods on the grinding process. International Journal of Machine Tools & Manufacture 2000;40:209-23. 8. Brinksmeier E, Minke E. High performance surface grindingthe influence of coolant on the abrasive process. Ann. CIRP 1999;42(1):367-70.
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TECHNICALLY speaking 9. Ramesh K, Yeo SH, Zhong ZW, Sim KC. Coolant shoe development for high efficiency grinding. Journal of Materials Processing Technology 2001; 114:240-5. 10. Ramesh K, Huang H, Yin L. Analytical and experimental investigation of coolant velocity in high speed grinding. International Journal of Machine Tools 8~ Manufacture
2004;44:1069-76. ABOUT THE AUTHORS Zhentao Shang is a PhD candidate in mechanical engineering at Hunan University in China. He is currently working at the University of Queensland as a visiting scholar. His research is in the field of abrasive machinin~ including high speed grinding~ truing and dressing technologies and coolant supply technologies. He can be reached via e-mail at [email protected], cn.
Dr. Han Huang # a reader in mechanical engineering at the University of Queensland in Australia. He has many years of research and working experiences in the field of abrasive machining. His current research interests include micromachinin~ high-efficiency grinding~ ecologically fi4endly machinin~ ultra-precision grinding~ and polishing and robotic machining. He can be reached via e-mail at [email protected].
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Kun Tang isa PhD candidate in mechanical enLnneering at Hunan University in China. His research interests are in thefield of abrasive machining. He can be reached via e-mail at [email protected]. Prof. Shaohui Yin is currently working at the National Engineering Research Centre for High Efficiency Grinding at Hunan University. His research areas include ultraprecision grinding and micromanufacturing. He can be reached via email at [email protected]. www.metalfinishing.com
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May 2008 1metalfinishing 121
, ) )c.~ xl,
10
Coolant Effect on Grinding Performance in High-Speed Deep Grinding of 40Cr Steel
H
igh-speed deep grinding (HSDG) technology was developed based on high-speed and creep-feed grinding techniques. 1-3 What mainly distinguishes HSDG from creep-feed grinding is its employment of a significantly higher wheel speed. Because the higher wheel speed results in a decrease in the undeformed chip thickness, HSDG is thus capable of achieving high stock removal rates and producing a high surface quality throughout the workpiece.46 However, the increase in wheel speed leads to the formation of a strengthened air barrier around the grinding wheel periphery, which is a great obstacle to the impinging of coolant into the grinding zone. 78 Additionally, the higher wheel speed will also generate greater grinding heat in the grinding zone, thus resulting in a higher temperature.' This increases the risk of thermal damage on the workpiece, such as burns and cracks, especially when grinding metals and alloys. In order to take advantage of the full potential of HSDG technology, effective cooling must be employed. Great research efforts have been directed toward investigating effective coolant supply technologies for the HSDG process.71° Previous works focused on the development of coolant nozzles for high-speed grinding, which could block the air barrier formation and help smoothly guide the coolant May 2008 1metalfinishing I 16
entering the grinding zone. There are several drawbacks regarding these nozzles. First, a gap between the wheel and the air-wiper in the nozzle still exists, which affects the coolant supply when operating at an extremely high speed. Second, the air blocking alters the coolant flow direction, thus resulting in an increase of 30-50% in spindle power. Third, special grinding wheels are required if there is direct contact between the wheel and the air wiper. This article will report on the development of a "closed" coolant shoe, which can overcome the limitations of previous coolant nozzles, and the effect of the new nozzle on the grinding performance in HSDG of 40Cr steel.
0
-6
Figure 1: Schematic illustrations of (a) conventional L-type nozzle, (b) closed Y-type nozzle, and (c) the detailed layout of the closed Y-type nozzle. (1) Grinding wheel; (2) steel cover; (3) rubber seal; (4) nozzle body; (5) hinge; and (6) adjustable blocker.
~
30 215
o" ~o
N
~
5 ,
~o 100
, l -e--L.tTPe
150 200 6r&ndinl~ speed ( ~ )
250
150 200 C,rir'~Ltnll speed (.,/s)
2150
Figure 2A 120 ~100
g
CLOSED Y-TYPE NOZZLE
Figure i shows the comparison of the conventional L-type nozzle and the detailed layout of the newly developed nozzle. As illustrated in Figure 1A, the L-type nozzle has only one orifice. The Y-type nozzle shown in Figure 1B has two orifices. The flow directions of the two orifices have an angle of 60 °, hence its name as "Y-type" nozzle. Figure 1C shows the detailed structure of the "closed" Y-type nozzle. "Closed" here refers to the nearly enclosed cavity formed by
t~ ~ 4o '~ 20 0 100
Figure 2B Figure 2: (A) Specific vertical force and (B) specific horizontal force are plotted as a function of wheel speed. Depth of cut = 1.7 mm; feed rate = 2,000 mm/min.
Table 1: Chemical Composition of 40Cr Steel (wt. %)
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TECHNICALLY speaKing the wheel (1), the rubber seal (3) and the nozzle body (4). The working principle of the nozzle is listed as follows: 1. The m o m e n t u m of coolant from the upper orifice counteracts with the airflows surrounding the wheel, which blocks the air circulating in the grinding zone and allows the coolant to enter the enclosed cavity. Additionally, the coolant from the upper orifice can clean out the wheel as well. 2. Coolant from the lower orifice is mainly sprayed into the grinding zone, functioning like the conventional coolant supply. 3. There is a gap between the wheel and the lower orifice, which acts as the third orifice, so coolant in the enclosed cavity can flow out from this orifice, whose direction can be altered to the grinding zone by the adjustable blocker (6).
EXPERIMENTALDETAILS All the grinding tests were conducted on a super-high-speed surface grinder developed by the National
Software for Finishers Visual Shop The Go/d Standard of job shop software for Finishers / Coaters.
Over 275 installations! Includes: Quotes • Orders • Certs • Process Masters • Expediting, Scheduling • Tracking • Shipping , Pricing , Invoicing • A / R • O n T r u c k Signature Signoff , UPS
Shipping , Sales Analysis , Pictures , Security • Inventory , Visual Net • Plant Messaging • Production Reports, and more.
Visual Shop- works for You!
,~
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, i too
O, 80
"ii
O. 70
1,2
1.6
*=
0.50
i
111
0.60
~" 0.4.0 o 0,30
~ 0.20 O. I0
,
O,00 2.0
2.4
I00
Depth of cat cam)
Figure 3A
, I -'=-- L.t 7pe
150 200 Grin~.r~ Speed (IJs)
250
Figure 4: Ground surface roughness is plotted as a function of wheel speed. Depth of cut = 1.7 mm; feed rate = 2,000 mm/rnin
25
0.60 15
~
, o ; NIO
0.50
= 0.4o 0 3O ~0.20 1.6 2.0 Depth of cut cam.)
1.2
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0.10 0. 00 1.2
Figure 3B
, I -=--L type 1.6 2.0 2.4 Depth ot c,.'t ( n )
Figure 3: (A) Specificvertica[ force and (B) specific horizonta[ force are plotted as a function of depth of cut. Grinding speed = 180 m/s; feed rate = 2,000 ram/rain.
Figure S: Ground surface roughness is plotted as a function of depth of cut. Grinding speed = 180 m/s; feed rate = 2,000 mm/min.
Engineering Research Centre for High-Efficiency Grinding in China. The spindle power of the machine was 40 kW, which enabled our group to run a wheel of 350 mm in diameter up to 24,000 rpm. 40Cr steel was selected as the workpiece
material, and its chemical composition is shown in Table 1. The workpieces were 30 mm long, 7.5 mm wide, and 15 m m thick. The grinding occurred on a 30 x 7.5 m m 2 surface. We used an electroplated cubic boron nitride (CBN) wheel of
Metal Recovery Specific Advantages of Metal Recovery
>Recovery Rates >Includes cyanide Greater than 95%. destruction while >Break the chelating reclaiming or agents that often tie removing metals. up metals. Other Wastewater Solutions Offered by Light Environmental Chromox Electrocoagulation www.liqhtenvironmental.com
Ph" 8 1 6 . 5 3 7 . 9 1 9 0
Acid R e g e n e r a t i o n
Ion Exchange Electrowinning
Email:[email protected]
................................................. Fax: 8 1 6 . 5 3 7 . 9 1 1 3
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May 2008 1metalfinishing I 17
TECHNICALLY speaking
2.50 2.00
~I.00
!
~
0.50 O.O0
Grindii~g Speed (m/s)
mesh size of 120 that had a diameter of 350 mm and a width of 16 mm. An upward grinding mode was employed. The table feed rate was fixed at 2,000 mm/min, and wheel speeds and depths of cut varied. Grinding tests were carried out using the closed Y-type nozzle and the conventional L-type nozzle, respectively. Grinding forces were monitored using a dynamometer (Kistler 9257B). The surface roughness was measured using a profilometer (Hommelwerke T8000). Surface topographies were examined using a scanning electron microscope (JSM-5610LV).
Figure 7: The maximum depths of cut prior to the onset of thermal damage obtained using the two nozzles. Grinding speed = 180 m/s; feed rate = 2,000 mm/min.
Figure: 6A
Figure: 6B
RESULTS AND DISCUSSION
Figure 6: SEM micrographs and photos of the surfaces ground using (A) the dosed Y-type nozzle and (B) the conventiona| L-type nozzle. Grinding speed = 180 m/s; feed rate = 2,000 mm/min; and depth of cut = 1.7 mm.
Grinding Forces: Figure 2 shows the effect of wheel speed on a specific grinding force when both the depth of cut and the feed rate of the workpiece were kept unchanged. It illustrates that both the specific vertical and horizontal forces decrease with an increase in wheel speed. It is well documented that in high-speed grinding, an increase in wheel speed leads to a reduction in the maxi-
mum undeformed chip thickness, 1 thus resulting in a decrease in grinding forces. Figure 3 shows the effect of depth of cut on the specific grinding force. It is seen clearly that the depth of cut has insignificant influence on the forces. This may be attributed to the relatively small variation in depth of cut. The thermal damage in the high-speed grind-
ing of 40Cr steel was sensitive to the depth of cut, especially when the Ltype nozzle was used, which significantly limited the range of selection for depth of cut. In Figures 2 and 3, it is clearly seen that both specific vertical and horizontal grinding forces using the Ytype nozzle are greater than those using the L-type nozzle for the same grinding conditions. It is worthy to point out that for the conventional L-type nozzle, the ground surfaces were thermally damaged. This suggests that when using the L-type nozzle, the poor cooling effect led to a higher temperature in the grinding zone and hence the thermal damage caused on the ground surfaces. As a consequence, the workpiece material was softened, thus resulting in a decrease in grinding force. SURFACE TOPOGRAPHIES
Figures 4 and 5 show the average roughness of the ground surfaces,
scrubbers to clean up the highly visible NOx orange brown plume from metal solver @ bionomicind.com finishing operations. www.bionomicind.com • Safe to Handle and Use-contains no toxic sulfides and does not liberate dangerous BIONOMIC hydrogen sulfide gas at lower pH use levels industries • Highly Effective-can be used to clean scrubber emissions resulting from bright dip, etching, and pickling operations 800-311-6767 (USA) FAX: 201-529-0252
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TECHNICALLY speaKing plotted as a function of wheel speed and depth of cut, respectively. In Figure 4, an increase in wheel speed resulted in a better surface finish. As mentioned earlier, an increase in wheel speed leads to a decrease in chip thickness; therefore, it is expected that the grinding grooves produced were shallower and the surface roughness value was smaller. Again, there was little effect of depth of cut on the surface roughness for the grinding conditions employed, as shown in Figure 5. For all the grinding conditions used, the surface roughness values obtained using the closed Y-type nozzle were smaller than those obtained using the conventional L-type nozzle, as shown in Figures 4 and 5. This is because the burns and cracks generated on the workpiece, due to the poor cooling effect when using the L-type nozzle, deteriorated the surface finish. Figure 6 shows two SEM micrographs and photos of the typical ground surfaces generated using the closed Y-type nozzle and the L-type nozzle respectively, while the rest of the grinding conditions remained the same. It is evident in Figure 6A that the surface ground using the L-type nozzle has cracks and rough plowing grooves near the thermally damaged region. The localized burn is severe and introduces mismatch of strain between hard oxide inclusions. In Figure 6B, when the closed Y-type nozzle was used, no burns and thermal damages were observed on the ground surface, demonstrating excellent surface integrity. MAXIMUM DEPTH OF CUT PRIOR TO THE ONSET OF THERMAL DAMAGE Figure 7 shows the comparison of the maximum depths of cut for the onset of thermal damage obtained when using these two respective nozzles. When grinding 40Cr steel at a high speed of 180 m/s, the L-type nozzle did not function well, as thermal damage was evidently observed on the ground surface when the depth of cut was only at 0.1 mm. Apparently, the application of the closed Y-type nozzle significantly improved the coolant supply to the grinding zone. The maximum depth of cut used prior to the onset of thermal damage is 2.3 mm, considerably greater than that using the L-type nozzle. The results suggests that without the effective coolant supply, it is impossible to employ HSDG technology for 40Cr steels. CONCLUSIONS The closed Y-type nozzle has been successfully developed for high-speed deep grinding of 40Cr steel. The new nozzle used the coolant flow jet from the upper orifice to wipe the air barriers around the wheel periphery at high speeds, which allowed the coolant from the lower orifice to enter the grinding zone and effectively remove the grinding heat. Compared to the www.meta[finishing.com
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TECHNICALLY
under its KeyResearch Project Scheme (10421), the Australia Research Council under the Discovery Project Scheme (DP0557349), and the Australia-China Science Linkage Program (CN070077).
s p e a k i n g
conventional L-type nozzle, the new nozzle significantly improves grinding performance and the ground surface quality because:
NOTES 1. Tawakoli T. High Efficiency Deep Grinding. London: Mechanical Engineering Publications Ltd., 1993. 2. Huang H, Liu YC. Experimental investigations of machining characteristics and removal mechanisms of advanced ceramics in high speed deep grinding. International Journal of Machine Tools ~ Manufacture 2003;43(8): 811-23. 3. Huang H. Machining characteristics and surface integrity ofyttria partially stabilized zirconia in high speed deep grinding. Materials Science and Engineering 2003;A345:155-63. 4. Ramesh K, Huang H. Burr con-
1. The ground surface roughness obtained using the Y-type nozzle was much smaller than that obtained using the conventional L-type nozzle; and 2. The maximum depth of cut prior to the onset of grinding thermal damage for the Y-type nozzle was 23 times higher than that for the conventional L-type nozzle. ACKNOWLEDGEMENTS The authors would like to acknowledge the experimental assistance of Mr. G.H. Zhang at Hunan University. This project is financially supported by the Ministry of Education, China,
trolled grinding using wheel speed parameter. Metal Finishing 2003;101:57-61. 5. Huang H, Yin L. Grinding characteristics of engineering ceramics in high speed regime. International Journal of Abrasive Technology 2007;1(1):78-93. 6. Yin L, Huang H, Ramesh K, Huang T. High speed versus conventional grinding in high removal rate machining of alumina and alumina-titania. International Journal of Machine Tools & Manufacture 2005;45(6): 897-907. 7. Ebbrell S, Wooley NH, Tridimas YD. The effects of cutting fluid application methods on the grinding process. International Journal of Machine Tools & Manufacture 2000;40:209-23. 8. Brinksmeier E, Minke E. High performance surface grindingthe influence of coolant on the abrasive process. Ann. CIRP 1999;42(1):367-70.
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TECHNICALLY speaking 9. Ramesh K, Yeo SH, Zhong ZW, Sim KC. Coolant shoe development for high efficiency grinding. Journal of Materials Processing Technology 2001; 114:240-5. 10. Ramesh K, Huang H, Yin L. Analytical and experimental investigation of coolant velocity in high speed grinding. International Journal of Machine Tools 8~ Manufacture
2004;44:1069-76. ABOUT THE AUTHORS Zhentao Shang is a PhD candidate in mechanical engineering at Hunan University in China. He is currently working at the University of Queensland as a visiting scholar. His research is in the field of abrasive machinin~ including high speed grinding~ truing and dressing technologies and coolant supply technologies. He can be reached via e-mail at [email protected], cn.
Dr. Han Huang # a reader in mechanical engineering at the University of Queensland in Australia. He has many years of research and working experiences in the field of abrasive machining. His current research interests include micromachinin~ high-efficiency grinding~ ecologically fi4endly machinin~ ultra-precision grinding~ and polishing and robotic machining. He can be reached via e-mail at [email protected].
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Kun Tang isa PhD candidate in mechanical enLnneering at Hunan University in China. His research interests are in thefield of abrasive machining. He can be reached via e-mail at [email protected]. Prof. Shaohui Yin is currently working at the National Engineering Research Centre for High Efficiency Grinding at Hunan University. His research areas include ultraprecision grinding and micromanufacturing. He can be reached via email at [email protected]. www.metalfinishing.com
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